From: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
To: Sebastian Reichel <sebastian.reichel@collabora.com>,
Michael Turquette <mturquette@baylibre.com>,
Stephen Boyd <sboyd@kernel.org>,
linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org
Cc: Christopher Obbard <chris.obbard@collabora.com>,
David Laight <David.Laight@ACULAB.COM>,
kernel@collabora.com
Subject: Re: [PATCH v2 2/2] clk: divider: Fix divisions
Date: Mon, 29 May 2023 10:50:51 +0200 [thread overview]
Message-ID: <66d9eaa2-4eb5-e9d1-cc76-0e0b68be44ca@collabora.com> (raw)
In-Reply-To: <20230526171057.66876-3-sebastian.reichel@collabora.com>
Il 26/05/23 19:10, Sebastian Reichel ha scritto:
> The clock framework handles clock rates as "unsigned long", so u32 on
> 32-bit architectures and u64 on 64-bit architectures.
>
> The current code pointlessly casts the dividend to u64 on 32-bit
> architectures and thus pointlessly reducing the performance.
>
> On the other hand on 64-bit architectures the divisor is masked and only
> the lower 32-bit are used. Thus requesting a frequency >= 4.3GHz results
> in incorrect values. For example requesting 4300000000 (4.3 GHz) will
> effectively request ca. 5 MHz. Requesting clk_round_rate(clk, ULONG_MAX)
> is a bit of a special case, since that still returns correct values as
> long as the parent clock is below 8.5 GHz.
>
> Signed-off-by: Sebastian Reichel <sebastian.reichel@collabora.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
next prev parent reply other threads:[~2023-05-29 8:51 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-26 17:10 [PATCH v2 0/2] Fix 64 bit issues in common clock framework Sebastian Reichel
2023-05-26 17:10 ` [PATCH v2 1/2] clk: composite: Fix handling of high clock rates Sebastian Reichel
2023-05-29 8:50 ` AngeloGioacchino Del Regno
2023-06-13 0:10 ` Stephen Boyd
2023-06-13 12:14 ` Maxime Ripard
2023-06-13 18:25 ` Stephen Boyd
2023-06-14 10:28 ` Maxime Ripard
2023-05-26 17:10 ` [PATCH v2 2/2] clk: divider: Fix divisions Sebastian Reichel
2023-05-29 8:50 ` AngeloGioacchino Del Regno [this message]
2023-06-13 0:41 ` Stephen Boyd
2023-06-13 8:05 ` David Laight
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