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[2003:e4:1f4b:7100:f22f:74ff:fe1f:3a53]) by smtp.gmail.com with ESMTPSA id h26-20020a170906261a00b00992f8110a2bsm2526819ejc.150.2023.07.12.05.31.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 12 Jul 2023 05:31:45 -0700 (PDT) Date: Wed, 12 Jul 2023 14:31:43 +0200 From: Thierry Reding To: Guiting Shen Subject: Re: [PATCH v3] pwm: atmel: Enable clk when pwm already enabled in bootloader Message-ID: References: <20230711200905.6464-1-aarongt.shen@gmail.com> <20230711203017.cdfe2nrjx7lt25tm@pengutronix.de> <90830c22-0437-591e-cee0-67b16214bc55@gmail.com> MIME-Version: 1.0 In-Reply-To: <90830c22-0437-591e-cee0-67b16214bc55@gmail.com> User-Agent: Mutt/2.2.10 (2023-03-25) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20230712_053148_046238_D8ACAC53 X-CRM114-Status: GOOD ( 24.27 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-pwm@vger.kernel.org, alexandre.belloni@bootlin.com, linux-kernel@vger.kernel.org, Uwe =?utf-8?Q?Kleine-K=C3=B6nig?= , claudiu.beznea@microchip.com, linux-arm-kernel@lists.infradead.org Content-Type: multipart/mixed; boundary="===============1822619240728610954==" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org --===============1822619240728610954== Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="eFQATVRlcI61GrFj" Content-Disposition: inline --eFQATVRlcI61GrFj Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jul 12, 2023 at 09:45:08AM +0800, Guiting Shen wrote: > On Wed, Jul 12, 2023 at 04:30:17AM GMT+8, Uwe Kleine-K=C3=B6nig wrote: > > Hello, > >=20 > > On Wed, Jul 12, 2023 at 04:09:05AM +0800, Guiting Shen wrote: > >> +static int atmel_pwm_enable_clk_if_on(struct atmel_pwm_chip *atmel_pw= m) > >> +{ > >> + unsigned int i; > >> + int err; > >> + u32 sr; > >> + > >> + sr =3D atmel_pwm_readl(atmel_pwm, PWM_SR); > >> + if (!sr) > >> + return 0; > >> + > >> + for (i =3D 0; i < atmel_pwm->chip.npwm; i++) { > >> + if (!(sr & (1 << i))) > >> + continue; > >> + > >> + err =3D clk_enable(atmel_pwm->clk); > >> + if (err) { > >> + dev_err(atmel_pwm->chip.dev, > >> + "failed to enable clock: %pe\n", ERR_PTR(err)); > >=20 > > Here you leak possibly a few enables. While it's not likely that the > > (say) third enable goes wrong, it's also not that hard to handle?! >=20 > The driver used the enable_count member of struct clk_core to count the > PWM channels(4 channels). It will enable hardware clock only when one of > the PWM channels becomed on from all PWM channels off which maybe return > error. And in second/third/fourth times to clk_enable(), it just > increased the enable_count of struct clk_core which would never return > error. >=20 > It maybe confused at first time to view the code. > Do it need to add something like that: ? >=20 > for (i =3D 0; i < atmel_pwm->chip.npwm; i++) { > if (!(sr & (1 << i))) > continue; >=20 > err =3D clk_enable(atmel_pwm->clk); > if (err) { > dev_err(atmel_pwm->chip.dev, > "failed to enable clock: %pe\n", ERR_PTR(err)); >=20 > for (i =3D 0; i < cnt; i++) > clk_disable(atmel_pwm->clk); > return err; > } > cnt++; You can also achieve this by decrementing i back to zero, that way you avoid the additional variable and you get a more natural unwinding of what you did before. So something like: while (i--) clk_disable(atmel_pwm->clk); should do the same thing. Thierry --eFQATVRlcI61GrFj Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEiOrDCAFJzPfAjcif3SOs138+s6EFAmSunS8ACgkQ3SOs138+ s6E41RAAovk3sb2LqH5DqsSa6g5cHTX0O0rUtwg6WYnUd/4aa6/pk17jxeGQ3Yqu DTB+i0g2WT5DzdL6kWo4fDiKgbujIL90zOunkq0JarZ/E+f7n6TrN3RM4hzcSIPs n/ad6mfv9/mx/iGvF/Xdt1Ujr8jMcQTyv2/5Ok6b+t6VML5RLpOhatKCaijznK2G YIiXb8U+h6cVP27TLpdb3BOqb9eCWkXKMX2nkvkS5ugsctqufkg+r5rjzO8Q/PFw rnXTyTuntaXrqaWYrN91SP8aZwtYMgb/7avt2/BDWjLEam8d8lP31q41B8sQuPCn PBDSWpAD4LI/S/CP+8AyvAKRBkK9UlIW2Qcna28jmRTjdHsypf5B+SIejYwJQbg3 uZFsWf0M0bvRBTzPYIeDXzuGBqe5X9qgq5VztZ3MmMG6GsY6E5Nkiv8yb16fg/aV IUSSMVdPXP7IK3JosFMMdrrZLm3SMYhJDHN3D1xYL2ICYXuwfLYdQ9SB/diLlMRW Pn+BBQ+KlVLpooxbAS78kKfF27/hRykVEUNsO7ZUy9V/Pq4tPoPfDdSOo/m6oPzT fmtHRdHyMX1eHIvi/xM0wzJYZTED0I+rbAVZ9xgtrVO/0icpZE54p9XLzuqiNs/a SVfwWqCc/PWWicB3sjQ7/iEz6tVdY9hvJ65vES2FTJamznAteH8= =Bllm -----END PGP SIGNATURE----- --eFQATVRlcI61GrFj-- --===============1822619240728610954== Content-Type: text/plain; charset="us-ascii" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit Content-Disposition: inline _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel --===============1822619240728610954==--