From mboxrd@z Thu Jan 1 00:00:00 1970 From: Faiz Abbas Subject: Re: [PATCH v2] dwc: dra7xx: Print link state to console for debug Date: Mon, 6 Nov 2017 08:26:29 +0530 Message-ID: References: <1508417009-30869-1-git-send-email-faiz_abbas@ti.com> <9378c5c9-381d-4c40-3290-f7e3720792ba@ti.com> <063D6719AE5E284EB5DD2968C1650D6DD009C62B@AcuExch.aculab.com> <53ed97ab-ed02-23be-0ce9-e79f2aaac979@ti.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-pci-owner@vger.kernel.org To: David Laight , "kishon@ti.com" Cc: "bhelgaas@google.com" , "linux-omap@vger.kernel.org" , "linux-pci@vger.kernel.org" , "linux-kernel@vger.kernel.org" List-Id: linux-omap@vger.kernel.org On Monday 30 October 2017 02:18 PM, Faiz Abbas wrote: > > > On Thursday 26 October 2017 01:29 PM, Faiz Abbas wrote: >> David, >> >> On Thursday 19 October 2017 06:56 PM, David Laight wrote: >>> From: Faiz Abbas >>>> Sent: 19 October 2017 14:09 >>>> On Thursday 19 October 2017 06:13 PM, Faiz Abbas wrote: >>>>> Enable support for printing the LTSSM link state for debugging PCI >>>>> when link is down. >>>>> >>>>> Signed-off-by: Faiz Abbas >>>>> --- >>>>> v2: >>>>> 1. Changed dev_err() to dev_dbg() >>>>> 2. Changed static char array to static const char * const >>>>> 3. format changes >>>>> >>>>> drivers/pci/dwc/pci-dra7xx.c | 48 ++++++++++++++++++++++++++++++++++++++++++++ >>>>> 1 file changed, 48 insertions(+) >>>>> >>>>> diff --git a/drivers/pci/dwc/pci-dra7xx.c b/drivers/pci/dwc/pci-dra7xx.c >>>>> index 34427a6..0e70e77 100644 >>>>> --- a/drivers/pci/dwc/pci-dra7xx.c >>>>> +++ b/drivers/pci/dwc/pci-dra7xx.c >>>>> @@ -98,6 +98,45 @@ struct dra7xx_pcie_of_data { >>>>> >>>>> #define to_dra7xx_pcie(x) dev_get_drvdata((x)->dev) >>>>> >>>>> +static const char * const state[] = { >>>>> + "DETECT_QUIET", >>> ... >>>>> + "RCVRY_EQ3" >>>>> +}; >>>>> + >>>>> static inline u32 dra7xx_pcie_readl(struct dra7xx_pcie *pcie, u32 offset) >>>>> { >>>>> return readl(pcie->base + offset); >>>>> @@ -118,6 +157,15 @@ static int dra7xx_pcie_link_up(struct dw_pcie *pci) >>>>> { >>>>> struct dra7xx_pcie *dra7xx = to_dra7xx_pcie(pci); >>>>> u32 reg = dra7xx_pcie_readl(dra7xx, PCIECTRL_DRA7XX_CONF_PHY_CS); >>>>> + u32 cmd_reg; >>>>> + u32 ltssm_state; >>>>> + >>>>> + if (!(reg & LINK_UP)) { >>>>> + cmd_reg = dra7xx_pcie_readl(dra7xx, >>>>> + PCIECTRL_DRA7XX_CONF_DEVICE_CMD); >>>>> + ltssm_state = (cmd_reg & GENMASK(7, 2)) >> 2; >>>>> + dev_dbg(pci->dev, "Link state:%s\n", state[ltssm_state]); >>> >>> Hmmm... GENMASK leaves by hunting header files...> Why not (cmd_reg >> 2) & 63 and explicitly define state[64] >>> to guarantee that you never print anything worse than a NULL >>> pointer. >> >> I'm not sure what you mean. Are you worried we might print something >> outside the array bounds? How is this easier to decipher than GENMASK? >> >>> >>>>> + } >>>>> >>>>> return !!(reg & LINK_UP); >>>>> } >>>>> >>>> >>>> I missed David's comment in v1. Will submit a new version. Please ignore. >>> >>> I've a 'neat' trick for generating strings that match constants. >>> You can get the compiler to do all the work for you: >>> (Assuming I've typed it correctly) >>> >>> #define LTSSM_DEFS(x) \ >>> x(DETECT_QUIET) \ >>> x(DETECT_ACT) \ >>> (continue for all the names) >>> >>> Define an enum with the named constants: >>> #define X(name) LTSSM_STATE_##name, >>> enum (LTSSM_DEFS(X) LTSSM_STATE_SIZE=64); >>> #undef X >>> >>> Array of strings: >>> #define X(name) [LTSSM_STATE_##name] = #name >>> static const char * const state_names[LTSSM_STATE_SIZE] = { LTSSM_DEFS(X) }; >>> #undef X >>> >>> David >>> >> >> So I implemented your idea and it looks like this: >> http://pastebin.ubuntu.com/25821834/ >> >> I don't know how much we gained by adding the trick. I still had to be >> careful not to be off by 1 when writing the list. Plus we are never >> saying anything like printk("%s", state[LTSSM_STATE_DETECT_QUIET]. Its a >> register read which is used to index the list array. >> >> Thanks, >> Faiz >> > > Gentle Ping. > Ping Again.